Hyperglycemia But Not Hyperinsulinemia Is Favorable for Exercise in Type 1 Diabetes: A Pilot Study

Abstract

Objective: To distinguish the effects of hyperglycemia and hyperinsulinemia on exercise-induced increases in Rd and endogenous glucose production (EGP) in type 1 diabetes.

Research design and methods: We studied six participants without diabetes and six participants with type 1 diabetes on three visits in random order for the following: euglycemia, low insulin (EuLoI); euglycemia, high insulin (EuHiI); and hyperglycemia, low insulin (HyLoI). Glucose fluxes were measured using [6,6-2H2] glucose before, during, and after 60 min of exercise.

Results: Rd increased (P < 0.01) with exercise within groups, while peak Rd during exercise was lower (P < 0.01) in participants with type 1 diabetes than participants without diabetes during all visits. In type 1 diabetes participants, EGP increased (P < 0.001) with exercise during EuLoI and HyLoI but not during EuHiI. This demonstrates that hyperinsulinemia, but not hyperglycemia, blunts the compensatory exercise-induced increase in EGP in type 1 diabetes.

Conclusions: The data from this pilot study indicate that 1) exercise-induced compensatory increase in EGP was inhibited in participants with type 1 diabetes with hyperinsulinemia but not with hyperglycemia; 2) in contrast, in participants without diabetes, exercise-induced increase in EGP was inhibited only during combined hyperinsulinemia and hyperglycemia. Taken together, these results suggest that low insulin coupled with euglycemia or modest hyperglycemia appear to be the most favorable milieu for type 1 diabetes during exercise.

© 2020 by the American Diabetes Association.

Figures

Figure 1

Schematic outline of the experimental design. The top panel shows three randomized visits with levels of glycemia and insulin infusion rates. The bottom panel shows the infusion patterns of 50% dextrose with [6,6-2H2] glucose, insulin, and [6,6-2H2] glucose during study visits.

Figure 2

Box plots of glucose (left), insulin (middle), and glucagon (right) concentrations measured during basal (Bas), pre-exercise (Pre), exercise (Ex), postexercise (Post), and end (End) periods, in participants without diabetes (light gray) and participants with type 1 diabetes (dark gray). Values are given during EuLoI (top), EuHiI (middle), and HyLoI (bottom panels) studies.

Figure 3

Box plots of EGP (left) and Rd (right panel) measured during basal (Bas), pre-exercise (Pre), exercise (Ex), postexercise (Post) and end (End) periods, in participants without diabetes (light gray) and participants with type 1 diabetes (dark gray). Values are given during EuLoI (top), EuHiI (middle), and HyLoI (bottom panels) studies.